The invention relates to a three-position, gas-insulated metal-clad electrical switch, the switch comprising two fixed break contacts each connected to a phase conductor, and a fixed ground contact together with a switching element that is movable in an axial direction to interconnect the fixed contacts.
Such an electrical switch is more particularly used for disconnection purposes when interconnecting phase conductors in a high-voltage installation. The switch is then generally referred to as a disconnector, and the three switching positions that can be achieved are conventionally:
opening the disconnector without grounding a phase conductor;
opening at the disconnector while grounding one of the two break contacts; and
closing the disconnector with the break contacts interconnected.
In the state of the art, one of the break contacts is generally grounded by a switching element that is different from the switching element that is used for interconnecting the break contacts. The resulting devices are thus relatively bulky. Furthermore, such devices cannot provide great flexibility in use, since once the switch has been installed, it is no longer possible to interchange that one of the two break contacts which can be grounded with the other break contact. A change to the grounding configuration then requires the switch to be reinstalled.
The object of the invention is to provide a three-position electrical switch of structure that is both simple and compact, and that can be used with different interconnection schemes without changing the external structure of the switch.
To this end, the invention provides a three-position, gas-insulated, metal-clad electrical switch inside a metal casing, the switch comprising first and second break contacts, a fixed grounding contact, and a switching element that is movable in an axial direction to interconnect said break contacts, wherein the first and second break contacts and said fixed grounding contact are superposed in said axial direction, and wherein said switching element is moved by means of a drive rod which passes through the fixed grounding contact, thereby enabling said switching element to occupy each of the three switching positions including a grounding position in which it connects the first break contact to the fixed grounding contact. With this disposition, the fixed break contacts and the ground contact are disposed substantially in alignment and can be received together with the switching element in a casing of metal cladding that is very compact in shape, the drive rod penetrating in sealed manner into the inside of the casing in order to move the switching element along said alignment of contacts.
In a particular embodiment of the switch of the invention, each break contact has a bore in which the switching element can penetrate.
In a particular embodiment of the switch of invention, the first break contact which is connectable to the fixed grounding contact by the switching element has a bore of length in the axial direction that is not less than the length of the switching element.
In a particular embodiment of the switch of the invention, the casing possesses two opposite openings on either side of the axial direction, each opening being provided with an electrically insulating support serving to hold an electrode on which one of said break contacts is fixed in a removable manner.
In a particular embodiment of the switch of the invention, each of the break contacts has a first arm which extends parallel to said axial direction and which is fixed to an electrode, and also a second arm which extends perpendicularly to the first arm to form an L-shape therewith, and into which the switching element penetrates, said break contacts being disposed in such a manner that the two L-shapes form a rectangle.
In a particular embodiment of the switch of invention, the first and second break contacts can be interchanged inside the casing by an operator in order to interchange that one of the two electrodes which can be grounded. This construction makes it possible to connect one or other of the electrodes to ground as a function of the selected interconnection scheme. As an option, a leak-proof inspection hatch of sufficient size can be provided in the casing of the switch to enable an operator to access the fixing means for fixing the break contacts to the electrodes.